This study will involve an in depth analysis of the physiologic mechanisms involved in induction and regulation of the release of histamine and other inflammatory mediators from human basophils and mast cells. Activation of the complement system by either the classical or alternative pathways leads to generation of C5a which has been shown to activate human basophils. Recently we have observed that a factor generated by human mononuclear cells can also induce basophil degranulation and histamine release. These reactions will be further explored and compared. In addition the response of human mast cells to these two factors will be explored using lung tissue. BIBLIOGRAPHIC REFERENCES: Complement-mediated release of histamine from human basophils. II. Biochemical characterization of the reaction. J.A. Grant, L. Settle, E. Whorton and E. Dupree. J. of Immunol. 117:450-456. 1976.